(a) Technical Field of the Invention
The present invention relates to an oil pump for a motorcycle, and in particular to a motorcycle oil pump that provides stable pumping of oil and enhanced durability.
(b) Description of the Prior Art
A motorcycle engine is provided with a lubrication system to ensure proper operation the engine. FIG. 1 of the attached drawings shows a conventional motorcycle engine lubrication system, which generally comprises an oil pan 10, an oil pump 11, and an oil passage 12. The oil pump 11 continuously draws and drives oil (which is a lubricant) contained in the oil pan 10 through the oil passage 12 to a variety of locations inside an engine E, such as rocker arm E3, crankshaft 2, piston E1, and internal wall of cylinder E2, for lubricating the engine E. The oil will eventually returns to the oil pan 10. The circulation is cycled to continuously lubricate the engine E.
Also referring to FIG. 2, the oil pump 11 is fixed to a crankshaft case 3 by threaded fasteners S to ensure stable positioning of the oil pump 11 and stable pumping of the lubricant. The oil pump 11 has a drive shaft 112 on which a drive gear 113 is mounted. An oil collector lid 114 is arranged at an end of the drive shaft 112, which is also fixed to the crankshaft case 3 by the fasteners S. The oil collector lid 114 is configured as an outward expanded pan-like member, functioning to preserve a certain amount of oil therein. When the engine E is inclined, the residual amount of oil inside the oil collector lid 114 can provide the drive gear 113 and the drive chain 22 with acceptable lubrication to maintain proper operation and minimize wearing thereof. Mounted outside the oil collector lid 114 a water pump 111 for driving cooling water. The water pump 111 has a shaft 1111 that is coaxially coupled to and thus rotatable in unison with the drive shaft 112. Thus, the water pump 111 is operatively coupled to the oil pump 11.
The oil pump 11 is driven by the drive chain 22. An end of the drive chain 22 is coupled to a transmission gear 21 of the crankshaft 2 and an opposite and coupled to the drive gear 113. When engine E is in operation, the chain 22 is driven by the crankshaft 2 to rotate the drive shaft 112, which in turns drives the oil pump 11. The oil pump 11 thus continuously pump the oil through the oil passages 12 for circulating the oil through the engine E, such as the rocker arms E3, the crankshaft 2, the pistons E1, and the internal walls of the engine cylinders E2, to lubricate the engine E.
Although the above described conventional oil pump 11 is effective in driving oil through and thus fully lubricating the engine E. However, the drive shaft 112 is basically supported by the oil pump 11 that physically engages an end portion of the shaft 112, which leaves an opposite end of the drive shaft 112 unsupported and forming a cantilevered construction. Although the cantilevered end of the shaft 112 is in contact with the shaft 1111 of the water pump 111, the shaft 1111 of the water pump 111 is itself of a cantilever arrangement. Since the load of the engine E is not fixes during the operation of the engine E, the rotational speed of the engine E is not fixed either, which often leads to oscillation of the drive shaft 112 due to abrupt change of rotational speed of the engine E, and vibration is included on the drive chain 22 by the oscillation of the drive shaft 112. Thus, enlarged gap between parts and noise caused thereby are generated. Further, the drive shaft 112 may be damaged by long-lasting vibration, leading to shortened service life.
It is thus desired to provide an oil pump that overcomes the above discussed drawbacks.